Lincoln Electric SVM153-A service manual Chopper Technology Fundamentals, 70-80VDC

E-7 E-7

THEORY OF OPERATION

Return to Section TOC

CHOPPER TECHNOLOGY

FUNDAMENTALS

The new era of welding machines such as the Commander 500, employ a technology whereby a DC source is turned on and off (chopped up) at high speed, then smoothed through an inductor to control an arc.

Hence the name “Chopper.” The biggest advantage of chopper technology is the high-speed control of the arc, similar to the inverter machines. A block diagram for this is as follows:

Return to Section TOC

Return to Master TOC

Return to Master TOC

EXTERNAL DC	SOLID STATE	INDUCTOR	ARC
SOURCE	SWITCH	AND DIODE

ARC

CONTROL

In this system, the engine drives a three-phase alter-	turning the switch on and off, current in the inductor
nator, which generates power that is rectified and	and the arc can be controlled. The following diagram
filtered to produce about 85VDC[?]. The current is	depicts the current flow in the system when the switch
applied through a solid state switch to an inductor. By	is open and closed.s

Return to Section TOC

Return to Master TOC

SWITCH

70-80VDC

DIODE

INDUCTOR

ARC

CURRENT WITH SWITCH OPEN

Return to Section TOC

Return to Master TOC

CURRENT WITH SWITCH CLOSED

When the switch is closed, current is applied through	varying the ratio of on time versus off time of the switch
the inductor to the arc. When the switch opens, current	(Duty Cycle),	the current applied to the arc is con-
stored in the inductor sustains flow in the arc and	trolled. This	is the basis for Chopper Technology:
through the diode. The repetition rate of switch closure	Controlling the switch in such a way as to produce
is 20Khz, which allows ultra-fast control of the arc. By	superior welding.

COMMANDER 500